Traditionally, a display system generated color images using red, green, and blue subpixels that can be combined to create a range of colors. In the physical world, colors are formed by relatively bright white light falling onto pigmented objects that absorb some portion of the light and reflect the rest. Non-color-saturated objects that are, for example, white or pastel may reflect substantially all of the light, thus appearing visually brighter than saturated color objects. Conversely, objects that form saturated colors absorb most of the light and reflect only a narrow band of the full spectrum of light falling on it, making the saturated-colored objects appear less bright. Statistically, saturated colors are relatively rare in the physical world. Furthermore, when saturated colors occur in nature, they are quite dark; bright saturated colors are rare in the physical world.
In manufacturing display systems that show images of the physical world, there is a trade-off between the brightness of the non-saturated colors and the color saturation gamut of the filtered backlight display. The more saturated the color filters, the richer the colors will appear in the image but at the expense of reduced overall brightness. If the filters are made less saturated to increase brightness of the display, the images will be brighter but the colors will not be as vibrant.
One of the ways to address this situation is by adding a white subpixel to the traditional RGB system to form a red, green, blue, and white (RGBW) system. The white subpixels significantly increase the brightness of the display system with non-saturated colors to effectively improve the perceived quality of the displayed images, most of which are of the physical world. FIG. 1 shows an example of a subpixel layout including R, G, B, and W subpixels. In one possible configuration of FIG. 1, subpixels 104 with vertical stripes represent “red” subpixels, subpixels 106 with diagonal stripes represent “green” subpixels, subpixels 102 with horizontal stripes represent “blue” subpixels, and unshaded subpixels 108 represent “white” subpixels.
The incorporation of white subpixels, while helpful for displaying images of the physical world, is not so advantageous when it comes to displaying texts. Texts, unlike most objects in the physical world, often come in saturated colors. The white subpixels would be minimally used or even turned off to display text in saturated colors. Hence, saturated-color texts, especially small fonts with single-pixel-wide strokes, suffer from having fewer subpixels during RGBW reconstruction. Specifically, the presence of un-used white subpixels with saturated-color images may cause resolution loss in diagonal direction and making the horizontal and vertical lines look dotty. A technique for using RGBW subpixels in a way that is advantageous for displaying text is desired.